PHILADELPHIA — Bernard Hopkins is circling a heavy punching bag, working up a sweat as he throws hard jabs, sharp combinations and a succession of pity-pat punches in rhythm.

“He looks solid. Strong,” says Oscar De La Hoya, the Hall of Fame boxer-turned-promoter, who is among a group of onlookers at Joe Hand Boxing Gym in North Philadelphia. “It’s amazing.”

Only the speckled gray in his beard offers any hint Hopkins is roughly two months shy of his 50th birthday. Otherwise, his body is sleek, fit and close to his 175-pound fighting weight. At an age when most boxers have long since retired, Hopkins is preparing to face one of the most vicious punchers in boxing: 31-year-old Sergey “Krusher” Kovalev of Russia. They will meet Nov. 8 at Boardwalk Hall in Atlantic City in a light heavyweight unification bout HBO will televise.

That Hopkins is the favorite in the eyes of many seems almost illogical. He became the oldest fighter to win a world title when he defeated Canadian Jean Pascal for the WBC light heavyweight belt in 2011 and looks to extend that mark as he turns a half-century on Jan. 19.

“No one expected me not only to become what I became, but they thought I’d be gone 10 or 15 years ago,” Hopkins said before his workout.

The challenger: Sergey KovalevAP

There will come a time when the Philadelphia native leaves the ring for good. When that happens, he deserves to be remembered not only as one of the greatest boxers ever, but one of the best athletes ever, period.

Naazim Richardson, Hopkins’ long-time trainer, put it this way:

“At his age, if he was in another sport, football, basketball or pitching shutouts and winning the World Series, he’d be on the front of every magazine, including Better Homes and Gardens. You’d be tired of seeing this dude. But our sport doesn’t get that respect.”

Defining the best athletes of all time is subjective and depends on the criteria. Longevity, number of championships, individual uniqueness, consistency, and the ability to excel under pressure all apply to Hopkins. Name another sport that is more taxing mentally and physically than boxing for 12 rounds? And name another athlete in any sport who has reigned at the top of his game the way Hopkins has in boxing?

He won the IBF middleweight title in 1994 and made a record 22 successful title defenses before capturing his first light heavyweight title by upsetting Antonio Tarver in 2006. He also has held a piece of the light heavyweight crown in four of the last five years. No, he might not be able to play basketball like Michael Jordan, run like Bo Jackson, hit a tennis ball like Martina Navratilova or win the decathlon. But doing what he’s doing at age 49 is worthy of Hopkins being at the top of anyone’s list of all-time great athletes.

Hopkins knocked out Trinidad at Madison Square Garden in September 2001. He was 36 then. He has since defeated De La Hoya, Tarver, Kelly Pavlik, Roy Jones, Pascal, and Tavoris Cloud, all world champions.

In his most recent fight last April, Hopkins out-pointed the previously unbeaten Beibut Shumenov of Kazakhstan for the WBA light heavy title. Hopkins credits a disciplined diet and lifestyle for his longevity. His confidence and ring smarts are also off the charts.

“Every athlete should be looking at what he does by living a healthier lifestyle,” De La Hoya said. “He’s becoming an example of what a human being and athlete should be doing.”

That’s easier said than done.

“It works for some. It won’t for others,” Richardson said. “Every young man can’t maintain that kind of discipline. Bernard is an extraordinary athlete.”